MAAP code analysis focusing on the fuel debris condition in the lower head of the pressure vessel in Fukushima-Daiichi Nuclear Power Station Unit 2

Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Cibula, M.*; Mizokami, Shinya*

Nuclear Engineering and Design, 404, p.112205_1 - 112205_21, 2023/04

https://doi.org/10.1016/j.nucengdes.2023.112205

Based on updated knowledge from plant-internal investigations, experiments and model simulations until now, the in-vessel phase of Fukushima-Daiichi Nuclear Power Station Unit 2 was analyzed using the MAAP code. In Unit 2, it is considered that the core material enthalpy was relatively low when it relocated to the lower plenum of the pressure vessel, then, cooled by the coolant and solidified there. Although the MAAP code tended to underestimate the degree of core-material oxidation during the relocation, this probable underestimation was compensated for by an existing study that was considered more reliable, so that more realistic debris conditions in the lower plenum could be obtained. Basic validity of the former prediction of the Unit 2 accident progression behavior was confirmed and detailed boundary condition for the later phase was provided. This boundary condition should be utilized for future studies addressing debris reheating process leading to lower head failure and debris relocation toward the pedestal.

Student and Young researcher's view of research on health physics and environment science

Miwa, Kazuji; Terasaka, Yuta; Ochi, Kotaro; Futemma, Akira; Sasaki, Miyuki; Hirouchi, Jun

Nihon Genshiryoku Gakkai-Shi ATOMO, 61(9), p.687 - 691, 2019/09

This report summarizes the contents of the session of the Health Physics and Environment Science Division, which was held in Atomic Energy Society of Japan 2019 Spring Meeting. In this session, six students and young researchers who engaged in the field of nuclear energy and radiation gave a lecture about health physics and environmental science research through their expertise. After the all presentations end, we took discussion time about the issues and future development in this field with all attendees. In this report, we summarized each lecture outline and discussion contents.

Data-base of bulk chemical compositions and modal compositions of Toki granitic body

Sakai, Toshihiro

JAEA-Data/Code 2018-006, 75 Pages, 2018/07

JAEA-Data-Code-2018-006.pdf:2.9MB
JAEA-Data-Code-2018-006-appendix(CD-ROM).zip:0.87MB

Data of bulk chemical compositions (major elements and trace elements) and/or of modal compositions of the Toki granitic body are compiled as a data-base for the purpose of improving geological and petrological basic information of the Mizunami Underground Research Laboratory Project and the Regional Hydrogeological Study Project. 696 rock samples are collected from the outcrops and boreholes of the Regional Hydrogeological Study Project, and 636 rock samples are collected from the Mizunami Underground Research Laboratory Construction Site. The analysis data of rock samples, as granitic rock samples, intrusive rock samples and crack filling samples, are attached three-dimensional position information to each thesis and report.

Study on the evaluation method to determine the radioactivity concentration waste generated from post-irradiation examination facilities

Hoshino, Yuzuru; Sakamoto, Yoshiaki; Muroi, Masayuki*; Mukai, Satoru*

JAEA-Technology 2015-015, 96 Pages, 2015/07

JAEA-Technology-2015-015.pdf:20.34MB

In order to dispose of the radioactive waste which generates from post-irradiation examination (PIE) facilities, the common evaluation method of radioactivity in wastes from PIE should be established by the actual data such as radioactivity values and the theoretical calculation. In this study, the radioactivity concentrations of 17 nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241, Cm-244) in combustible wastes stored in NUCLEAR DEVELOPMENT CORPORATION were measured from 3 samples and the radioactivity was calculated by ORIGEN-2 based on initial contents and operation record of the spent fuel. From the comparison of the obtained data by the radiological measurement with the calculated values, the subject to be solved for establishment of the radioactivity evaluation method for PIE was extracted.

Application of Laser-Induced Breakdown Spectroscopy (LIBS) analysis to molten alloy production process

Ozu, Akira; Tachi, Yoshiaki; Arita, Yuji*

Reza Kenkyu, 42(12), p.913 - 917, 2014/12

Laser-induced breakdown spectroscopy (LIBS) analysis has been applied to the molten alloy production process, in which simulated metals (Zr, Cu, Sm, Ce) are used instead of nuclear metallic fuels contained minor actinide (MA), with the aim of in-situ monitoring the elementary composition of the surface of the molten alloy in a chamber and vapor particles generated from the surface of the molten alloy. The variation in the ratio of elementary composition of the surface of the molten alloy in the crucible was successfully observed depending on temperature of the crucible. The elementary composition of the vapor particles appeared in the molten alloy chamber was also measured. The practical experimental results show that LIBS technique is very useful for investigating the elementary composition in the process and understanding the behavior of molten alloy in the crucible.

Effect of change of environmental conditions on the elemental composition of airborne dust

Miyamoto, Yutaka; Saito, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu

Journal of Radioanalytical and Nuclear Chemistry, 271(1), p.83 - 88, 2007/01

https://doi.org/10.1007/s10967-007-0110-8

Airborne dust samples were collected with a high-volume sampler at a fixed point in JAERI-Tokai for three years. Recently at JAERI-Tokai, a number of pine trees to arrest sand shifting was cut down. We analyzed the variation in elemental composition of the dust collected before and after felling the trees. It found, from the two-dimentional plots of ratio of elemental concentration such as Sc/Na-Cl/Na ratios, almost all samples consisted of mixture of sea-salt and soil. There were some differences between the elemental composition of the dust collected before and after felling the trees.

Evidence for p-process nucleosynthesis recorded at the solar system abundances

Hayakawa, Takehito; Iwamoto, Nobuyuki; Shizuma, Toshiyuki; Kajino, Toshitaka*; Umeda, Hideyuki*; Nomoto, Kenichi*

European Physical Journal A, 27(S1), p.123 - 128, 2006/03

https://doi.org/10.1140/epja/i2006-08-017-6

no abstracts in English

Oxygen potential measurements of fluorite-type ZrPuO by EMF method

Otobe, Haruyoshi; Nakamura, Akio; Yamashita, Toshiyuki; Minato, Kazuo

Journal of Nuclear Materials, 344(1-3), p.219 - 222, 2005/09

https://doi.org/10.1016/j.jnucmat.2005.04.045

Actinides-bearing zirconias are prominent candidate materials for various nuclear applications: targets for actinide transmutation, inert material fuels, radioactive waste forms, etc. In this study, the oxygen potential (g(O)) behavior of fluorite-type (F-type) ZrPuO has been measured by EMF method using the zirconia oxygen sensor. It was found that the g(O) values of F-type ZrPuO were about 150 kJ/mol higher than those of F-type PuO at the same oxygen-nonstoichiometric (O/M) values. The g(O) values of F-type ZrPuO were 50 kJ/mol lower than those of pyrochlore ZrPuO at the same O/M values. These results suggest that the g(O) behavior depends on the cation and anion ordering/disordering, in addition to the cation composition ratio (Zr/Pu).

Study on dissolution behavior of molten solidified waste

Mizuno, Tsuyoshi*; Maeda, Toshikatsu; Bamba, Tsunetaka*

JAERI-Conf 2005-007, p.225 - 229, 2005/08

https://jopss.jaea.go.jp/pdfdata/JAERI-Conf-2005-007.pdf

no abstracts in English

Characterization of 50L-scale solidified products yielded by melting treatment of miscellaneous solid wastes and evaluation of radioisotope tracer distribution

Nakashio, Nobuyuki; Nakashima, Mikio; Hirabayashi, Takakuni*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.279 - 287, 2004/09

https://doi.org/10.3327/taesj2002.3.279

Large-scale melting tests of simulated miscellaneous solid wastes were conducted to characterize solidified products (50L-drum size). Two heating modes were adopted in the tests: hybrid heating and induction heating modes. In the former, wastes were heated with both an induction furnace and a plasma torch, and in the latter, an electrically-conductive crucible was used with the induction furnace. Visual observation, chemical analysis and radioactivity measurements were conducted to the solidified products. It was found that the radioisotope distribution of solidified products was almost homogeneous. There was no remarkable deterioration in the solidified products subsequent to the leaching test.